Inhibition of hydrogen and oxygen recombination over amide-functionalized graphene and the enhancement of photocatalytic hydrogen generation in dye-sensitized AF-RGO/Pt photocatalyst dispersion

Photocatalytic hydrogen evolution (PHE) is a promising way to generate hydrogen driven by solar light. Noble metallic Pt is usually used as a co-catalyst to catalyze this reaction. However, Pt can also act as an active center for H-2 and O-2 recombination reverse reaction, which results in the low photocatalytic efficiency for H-2 generation. Herein, the H-2 and O-2 recombination can remarkably be inhibited by incorporating amide-functionalized groups onto graphene surface and edge, which act as the oxygen adsorbent site and reduce migration of O-2 molecules in the dye-sensitized PHE system. Theoretical studies verify that the adsorption energy of oxygen change remarkable due to orbital hybridization by N 2p in amide group with O 2p in O-2 molecule, leading to redistribution the electron structure of graphene, and change of electrical properties of sensitized matrix. By amide-functionalized graphene (AF-RGO), we achieved high H-2 evolution activity over AF-RGO/Pt nanohybrid catalyst under visible light irradiation. The quantum efficiency of AF-RGO/Pt (AF-RGO prepared at 140 degrees C) achieved 36.4% at 430 nm. This superior photocatalytic performance can be attributed to the repression of H-2 and O-2 recombination and the synergy of electrical properties. This work is helpful to design high active catalyst for solar hydrogen generation.